The present invention relates to an elastic coupling using rubber members, and is the elastic coup which is utilized between a driving shaft and a driven shaft and transmits a rotary force.
As for conventional elastic couplings, such couplings as shown in FIG. 1 and FIG. 2 are generally known: In a state of the elastic coupling shown in FIG. 1 wherein bands 7 are not yet attached. The coupling has three fixed wings 2 which individually extend radially with equiangular intervals from a flange 1 near the center of an axis, and bushes 3 which are each formed between individual said fixed wings are arranged on concentric circles, and elastic rubbers 4 interconnect these. In general, front ends of the wings 2 are arranged on the concentric circles, and the bushes 3 are, on the other hand, arranged on the concentric circles of a radius R.sub.2, which is slightly larger than a radius R.sub.1 extending to the front ends of the wings 2. In addition, a hole 5 for connection to a rotary shaft, which is not indicated in the Figures, is provided in each bush 3. Moreover, an axial hole 6 for connection to a spline is formed in the center of the flange 1 to be inserted and fixed to a spline shaft which is not shown in the Figures. A sign "a" shown in FIG. 1 indicates hollows.
In case that the elastic coupling is utilized as a coupling, it so devised that a stress which acts on the elastic rubbers 4 always acts on said rubbers when they are in a compressed state. This is to protect against the deterioration of the elastic rubbers 4 in their early stages which occurs when compressive stress and tensile stress act on said rubbers 4. Accordingly, in this example, the bushes 3 on the concentric circles can be fitted to the shaft with a slight push while directing them toward the center.
FIG. 2 shows an example when the rubbers are in a compressed state. In this case, semicircular bands 7 are first applied to them from the outside of the bushes 3, and then bolts 8 and nuts 9 are tightened so that the outward ends of the bushes 3 are pushed toward the center of the circle, and the radius (R.sub.2) between the outer surface of the bushes 3 and the center shown in FIG. 1 assumes a radius R.sub.o smaller than the radius R.sub.2. The radius R.sub.o which is formed by the semi-circular bands 7 is in a relationship of R.sub.2 &gt;R.sub.o &gt;R.sub.1. That is, by this extent, the radius extending to the outer surface of the bushes 3 is shortened, which can be easily understood by observing the deformation of the passages "a".
In this way, the elastic rubbers 4 between the bushes 3 having the reduced radius and the fixed wings 2 are precompressed at the time of fitting the coupling to the shaft, which leads to the prevention of the deterioration of said rubbers in their early stages. The process of reduction of the radius extending to the outer surface of the bushes 3 mentioned above is incidental to any elastic couplings. Just like this example, the bands 7 have to be applied to the bushes 3, and the bands 7 have to be tightened by bolts 8 and nuts 9, and when the fitting to the shaft is completed, the bands 7 have to be removed. Therefore, the operation efficiency is extremely impaired.
Although it is beyond the possibility that the coupling is utilized without removing the bands 7, if it is utilized with the bands 7 being attached, the bands 7 get out of line as soon as the rotation starts, because they are not fixed to the bushes 3, the fixed wings 2 and the like, which invites a serious danger. Moreover, as tightened portions of the bands 7 protrude from the circumference of the coupling, they produce abnormal sound in rotation. Thus, it is impossible to put it to practical use without removing the bands.